1. Field of the Invention
This invention relates to a vehicle body structure, and more particularly, to a mounting structure of a coupling member used to couple a rear portion of a front side member to a side frame member.
2. Description of the Related Art
There have been proposed various vehicle body structures for distributing the impact force, applied to front side members at the time of a front collision of a vehicle, to various portions of the vehicle body to thereby attain an impact-absorbing function. For example, a vehicle body structure has been proposed, in which rear portions of front side members are coupled through dash braces to side frame members such as A-pillars, side sills, or the like, so that the impact force applied to the front side members are distributed to the side frame members (see for example Japanese patent publication no. 3200853).
FIG. 4 is a sectional plan view showing a vehicle body structure disclosed in Japanese patent publication no. 3200853, in which a left side portion of the vehicle body is shown. The engine room R1 of the vehicle is separated from the vehicle compartment R2 by a dash panel 21 whose left end is joined to a side frame member 22. The dash panel 21 has a front face to which is joined a rear end of a front side member 23 having one side thereof coupled to a front end of a side member 24 fixed beneath the vehicle floor.
Also joined to the front face of the dash panel 21 is a dash cross member 25 which cooperates with the dash panel to form a closed cross-section and through which the rear ends of the left and right front side members 23 are coupled to each other. Further, a dash brace 26 is provided, which is joined to the rear face of the dash panel 21 so as to form a closed cross-section in cooperation with the dash panel and through which the rear end of the front side member 23 is coupled to the side frame member 22.
At the time of a front collision of the vehicle, the impact force applied to the front side members 23 from front is transmitted to the side members 24 and to the dash cross members 25, and also to the side frame members 22 through the dash braces 26. In this manner, the impact force is distributed to various portions on the side of the vehicle compartment R2, and the front side members 23 are deformed from their front ends, utilizing reaction forces generated in the various portions, whereby an impact-absorbing function is attained.
As apparent from FIG. 4, however, the dash brace 26 having such arrangement and shape as disclosed in Japanese patent publication no. 3200853 forms a ridge L22 which is independent of and is not directly continuous with a ridge L21 of the front side member. As well known, the impact force is mainly transmitted through the ridge L21 of the front side member 23 and the ridge L22 of the dash brace 26. In a case where the ridge L21 is discontinuous with the ridge L22, therefore, a deformation is caused at the discontinuous portion, so that the impact force cannot efficiently be transmitted from the front side member 23 to the dash brace and to the side frame member 22. As a result, a sufficient impact-absorbing function cannot be realized utilizing the reaction force generated in the side frame member 22.